This invention relates to a V-type multiple cylinder engine, and more particularly, to an intake apparatus for a V-type multiple cylinder engine which is adapted to distribute fuel from a fuel supplying device via an intake manifold.
A V-type multiple cylinder engine in which cylinder rows with a plurality of cylinders disposed in parallel are formed as a pair and are disposed in the form of an inclined V-shape has advantages that a degree of freedom of mounting on a vehicle is enhanced and that the engine room can be made compact since the overall engine height is reduced by a degree corresponding to the inclination of the cylinders. In addition, in a case where fuel is supplied by using a single fuel supply device, e.g., a carburetter or a single point injection, as a supply source via an intake manifold, thus making uniform the distribution of fuel into each cylinder and the arrangement of a compact intake apparatus can be attained since intake passages can be formed symmetrically from a trough of a V-shaped valley to both sides. As an apparatus having such an advantages, it may be provided intake apparatuses for V-type multiple-cylinder internal combustion engines disclosed in Japanese Patent Laid-Open Nos. 60258/1985 and 138265/1985.
Meanwhile, in an intake apparatus for an engine, a channel from a fuel supplying source to a combustion chamber is generally formed in such a manner that a recess is not formed from the top to the bottom. The reason for this is that if a recess is formed midway in the channel, fuel is supplied as a wall current in the form of a liquid since the atomization or vaporization of the fuel are not sufficiently attained during a low-temperature start or in an environment close to the same, so that the wall current flows backwardly at a rising gradient in the downstream of the recess and stagnates in the recess. The stagnated fuel is sucked into the combustion chamber at a stroke in the next step, i.e., during acceleration or the like when the amount of intake air is relatively large, the air-fuel ratio becomes over-rich, so that the smoothness of combustion becomes lacking, which results in faults such as the unsmoothness of driveability and an increase in the amount of exhaust of unburned products which contaminate the atmosphere.
This pushes up the overall height of the engine even in the case of the V-type engine which is advantageous in mounting on a vehicle, and hence there are cases where it becomes impossible to make sufficient use of the above-described advantages. In the intake apparatuses of the aforementioned Japanese Patent Laid-Open Nos. 60258/1985 and 138265/1985, branches of the intake manifold are arranged horizontally along the V-shaped valley, and a collecting section and a fuel supplying source are disposed laterally so as to restrain the overall height to a low level.
However, in an apparatus of conventional type, a collecting section of the intake manifold is disposed in a central portion of a V-shaped valley, and branches are extended with the collecting section as a center and set at least horizontally. In addition, as to a fuel supplying device and an air cleaner, an arrangement is adopted such that they are directly coupled above the collecting section to uniformly distribute the fuel in an ideal manner.
However, if the above-described arrangement is adopted, the overall engine height becomes high. A V-type engine essentially has an advantage in that the overall engine height can be made low by a portion in which the cylinders are inclined, so that the degree of freedom of mounting in a vehicle is large. However, in accordance with the request for making uniform the distribution of fuel, a described above, a problem arises in that it becomes impossible to make sufficient use of that advantage.
Among V-type multiple cylinder engines of a similar type, there is one in which a collecting section of the intake manifold is disposed laterally, and each branch is led out horizontally in parallel with a crankshaft and is connected to each intake port, so as to restrain the overall engine height to a low level (e.g., Japanese Patent Laid-Open No. 60258/1985 or 138265/1985). If an attempt is made by following that fashion to supply fuel from the fuel supplying device disposed laterally with respect to the collecting section arranged in the center, the overall engine height can be made low, but there is a problem in that an adverse effect is exerted to the uniformity of fuel distribution due to the directionality of an intake current.